The present invention relates to a thin-walled synthetic resin laminated body for liquid containers, and also to a method for manufacturing the same.
In many instances, containers for liquid cosmetics, liquid detergent or the like have been formed of relatively thick-walled synthetic resin or glass, and discarded after consumption of the contents. Needless to say, it is desirable to reduce the amount of wastes to the extent possible, in view of waste disposal environment which is progressively severe in recent years. Under such circumstances, it became popular to accommodate the contents into a simple bag-shaped container and thereby reduce the weight and volume of wastes. This type of bag-shaped container is manufactured, for example, by bonding two sheets of plastic films to each other at the peripheral regions of their inner surfaces and tightly sealing them after charging a liquid into the interior space. In use, a corner portion of the bag-like container is cut away to open the storage portion which is then compressed so as to discharge the contents.
However, this type of bag-shaped container has a poor shape-stability in itself, and it is therefore difficult to stably hold the container with the contents filled therein, or to readily and positively adjust the discharge amount and discharge direction of the contents, besides that the shape of the container is basically limited to a relatively simplex planer shape. Therefore, it would be desirable to provide a liquid container which can be used in more facilitated manner, having a higher freedom degree of design, capable of being readily formed into a desired three-dimensional shape suitable for the required use, and capable of being manufactured in a simple and inexpensive manner.
It is therefore a primary object of the present invention to provide a synthetic resin thinly laminated body and a manufacturing method therefor, that are capable of forming a liquid container satisfying the aforementioned demand.
To achieve the above-mentioned object, the present invention provides a thin-walled laminated synthetic resin body for a liquid container, comprising first and second thin-walled synthetic resin layers, each having a curved surface portion and a projection, said projection extending outwardly from a predetermined region at an edge of said curved surface portion, wherein said first and second layers are laminated to each other with said curved surface portions bulging out in the same direction, said first and second layers are integrated with each other at the edges of said curved surface portions and at edges of said projections, and said first and second layers are separable from each other at those regions other than said edges of the curved surface portions and projections so that said curved surface portion of one of said first and second layers is separated from the curved surface portion of the other of said first and second layers and reversed when a liquid is charged, causing said curved surface portions to bulge out in the opposite directions, respectively, and thereby defining an inner space for containing a liquid between said curved surface portions.
The present invention also provides a method for manufacturing a thin-walled, laminated synthetic resin body for a liquid container, comprising the steps of mutually laminating first and second layers each made of a thin-walled synthetic resin sheet and having a curved surface portion and a projection, said projection extending outwardly from a predetermined region at an edge of said curved surface portion, with said curved surface portions bulging out in the same direction, and integrating said first and second layers with each other at said edges of the curved surface portions and at edges of said projections so that said first and second layers are separable from each other at those regions other than said edges of the curved surface portions and projections, and charging a liquid and reversing said curved surface portion of one of said first and second layers by separating it from the curved surface portion of the other of said first and second layers, causing said curved surface portions to bulge out in the opposite directions, respectively, and thereby obtaining a laminated body in which an inner space for containing is defined by a liquid between said curved surface portions.
According to the present invention, the thin-walled synthetic resin laminated body has a sufficient shape stability which is afforded by the curved surface portions, so that the laminated body can be stably held when used as a liquid container filled with the contents, thereby enabling simple and assured adjustment of the discharging amount and direction. Also, the shape of the curved surface portions can be readily formed into a desired three-dimensional configuration depending on the application, with improved freedom degree of design, without limited to a relatively simplex planer shape of the conventional. The synthetic resin laminated body having the above-mentioned unique structure can be manufactured readily and at a low cost, with a conventional manufacturing system.
In a preferred embodiment of the present invention, both of the first and second layers have flanges extending along the edges of the curved surface portions and the projections, respectively, and the first and second layers are fused to each other at the flanges. Alternatively, it is also possible to arrange an adhesive layer between the flanges along the edges of the curved surface portions and the projections, respectively.
In another preferred embodiment of the present invention, there is provided a separation layer on a region of the laminated surface side of one of the first and second layers, which is exclusive of the edges of the curved surface portion and projection of the one of the first and second layers.
In another preferred embodiment of the present invention, the first and second layers are formed of synthetic resin sheets made of the same material, and the synthetic resin sheets are laminated to each other under a predetermined temperature difference so as to afford a separability from each other. When the first and second layers are formed of synthetic resin sheets made of the same material, there may be further provided a separation sheet of a different material interposed between the first and second layers at a region excluding the edges of the curved surface portions and projections of the first and second layers.
In another preferred embodiment of the present invention, the first and second layers are formed of synthetic resin sheets made of materials which are different from each other so that the different materials exhibit a separability from each other in a laminated state of the first and second layers.
In another preferred embodiment of the present invention, the first and second layers are made of a single synthetic resin sheet, and connected to each other in a configuration folded at those edges of the curved surface portions, which are positioned at an opposite side to the projections so that the folded edges form a bottom of the container filled with a liquid.
In another preferred embodiment of the present invention, at least one of the first and second layers has a rigidity (or, so-called shape stability) which is sufficient for maintaining the shape of the container at least when it is filled with a liquid.
In another preferred embodiment of the present invention, the projections of the first and second layers are designed to allow formation of a discharge port of a hollow cylinder shape. In this case, it is preferred to provide breakable portions for opening the discharge port at the projections of the first and second layers.
In another preferred embodiment of the present invention, the projections of the first and second layers are formed as an end portion for fitting a cap and/or nozzle unit thereto.